1. Technical Field
The present invention relates to reducing electromagnetic interference between conducting wires in close proximity to each other.
2. Description of Related Art
A common problem encountered in the use of conductive wiring for communications is the phenomenon of crosstalk. Crosstalk refers to electromagnetic interference between wires in close proximity to each other, resulting in degradation of signal quality. To reduce crosstalk, the wires must be arranged so that their respective electromagnetic fields cancel each other and produce a reduced composite radiation pattern.
A well-known method for reducing electromagnetic interference (including crosstalk) is twisted pair wiring. The twisting of the paired wires places their respective electromagnetic fields out of phase with each other. This phase difference causes the two fields to partially cancel each other, thereby reducing the composite field, and hence, crosstalk with other wires in the vicinity.
After twisted pairing, the next step, usually, is to take several twisted pairs of wire and twist them together into groups, and then twist the groups into a round cable. To reduce crosstalk between the pairs, a variety of lays (length of twist) are used for each pair to produce random conductor orientation. This random orientation places the electromagnetic field of each pair out of phase with the others, thereby reducing, but not eliminating, the possibility that one pair will interfere with another pair.
Though the random orientation caused by different twisting lengths is very useful in reducing crosstalk between twisted pairs, it does have its limitations. The phase differences between the different electromagnetic fields will usually result in destructive interference, reducing the strength of the composite field. In some cases, the random orientation may cause complete destructive interference, thereby eliminating all crosstalk. However, the randomness can work in the other direction and produce constructive interference, which will strengthen the composite electromagnetic field and exacerbate crosstalk.
The lack of control in random orientation limits the degree to which the composite electromagnetic fields, and resulting crosstalk, can be reduced. Therefore, a method for reducing crosstalk more precisely and effectively than random conductor orientation is desirable.
The present invention provides a wiring apparatus for reducing electromagnetic interference between conductive wires. Wire pairs are incorporated into rigid or flexible printed circuits to precisely control loop alignment and phase differences. This precise alignment helps to cancel radiated electromagnetic fields and reduce voltage polarities induced in nearby wires.
In one embodiment, a pair of parallel wires is aligned parallel to a second, twisted pair of wires. In another embodiment, two twisted pairs of wires, with identical loop lengths, are aligned parallel to each other and offset by exactly one half loop length. In a third embodiment, two twisted pairs of wires are aligned parallel to each other, in which one pair has a loop length that is an integer ratio of the other pair.